PHP: Find index of array in multidimentional array based on given value

Question

I am trying to set up a form to allow users to update data in a large JSON file. I have a form that allows the user to grab the 'event' they want and to edit it. When they click submit, it sends the data to a script that pulls the entire JSON file into an array. From there, I need the script to search through that array and find the index of the sub-array that has the same ID as the 'event' that has been edited. So if the user has edited the entry called "William Bradford born", I need the script to match the ID "american-ccincore-1411541230" and return 0 for that sub-array's index.

[
  {
     "id" : "american",
     "title" : "A Timeline of American Literature",
     "description" : "LENGTHY DESCRIPTIVE TEXT",
     "initial_zoom" : "50",
     "focus_date" : "1650-01-01 00:00:00",
     "size_importance" : "true",
     "timezone" : "-06:00",
     "min_zoom" : "20",
     "max_zoom" : "80",
     "image_lane_height" : "50",
     "display_zoom_level" : "1",
     "tags" : {
       "Puritan" : "0",
       "Enlightenment" : "0",
       "Romantic" : "0",
       "Transcendental" : "0",
       "Dark Romantic":  "0",
       "African American": "0",
       "American Indian": "0",
       "International" : "0"
     },
     "legend": [
       {
         "title": "Author event",
         "icon": "star_red.png"
       },
       {
         "title": "Publication event",
         "icon": "square_blue.png"
       },
       {
         "title": "Historical event",
         "icon": "triangle_green.png"
       }
     ],
     "events": [
       {
         "id": "american-ccincore-1411541230",
         "title": "William Bradford born",
         "description": "LENGTHY DESCRIPTIVE TEXT",
         "tags": "Puritan",
         "startdate": "1950-03- 00:00:00",
         "enddate": "1657-05- 00:00:00",
         "importance": "50",
         "date_display": "year",
         "link": "",
         "image": "https://www.csustan.edu/sites/default/files/ENGLISH/reuben/pal/chap1/bradford.gif",
         "icon": "star_red.png",
         "span_color": "#f66"
       }, {
         "id": "american-mforkner-1411364607",
         "title": "Church Mission Society",
         "description": "LENGTHY DESCRIPTIVE TEXT",
         "tags": "",
         "startdate": "1799-01-01 00:00:00",
         "enddate": "1799-01-01 00:00:00",
         "importance": "50",
         "date_display": "year",
         "link": "",
         "image": "http://webarchive.cms-uk.org/_images/tnsaies1.jpg",
         "icon": ".png",
         "span_color": "#ccc"
       }
     ]
  }
]

I've tried to adapt scripts suggested in a dozen or so posts here, but I can't get any to work in this particular situation. Thanks for any advice.

Answer 1

It's just a simple loop. The caveat is you need to distinguish between an answer of 0 and a failure to find the event you were looking for. I typically use false to indicate failure, but that means using === or !== for your comparison later.

function findEventIndexById($events, $target) {
    $retval = false;
    foreach($events as $index=>$oneEvent) {
        if ($oneEvent->id == $target) {
            $retval = $index;
            break;
        }
    }
    return $retval;
}

$foundIndex = findEventIndexById($data->events, $eventId);
if ($foundIndex !== false) {
     // ... do stuff here to $data->events[$foundIndex]
} else
    // ... report an error ...